Carpet Tile and Method of Manufacturing Same

ABSTRACT

The carpet tile system uses preferably Aluminum Hydroxide (Al(OH) 3 ) as a flame retardant in the secondary backing of the carpet tile or in the pre-coat adhesive on the primary backing, or alternatively uses Magnesium Hydroxide (Mg(OH) 2 ). The flame retardant has been optimized to interact with the other components of the system to produce a carpet tile that achieves flammability ratings that are comparable or superior to carpet tiles with more expensive pile fibers.

BACKGROUND OF THE INVENTION

This invention relates to carpet tiles, and in particular to carpet tiles which use relatively inexpensive fibers and achieve a flammability rating comparable to or better than the flammability rating of carpet tiles using more expensive fibers.

This invention primarily relates to carpet tiles which use a bitumen backing system. However, the invention may also improve the flammability of carpet tiles using other backing systems.

There are three principal synthetic fibers that are used in commercial carpet: nylon (polyamide), polyester and polypropylene. Nylon is the most expensive of the three fibers. One of the benefits of using nylon is that you can generally achieve a better flammability rating than with the other two. Today the majority (more than 90%) of carpet tile sold in North America is made from nylon fiber.

There are two kinds of polyester in common use, namely PET (polyethylene terephthalate) and PTT (polytrimethylene terephthalate). There are two kinds of nylon in common use: nylon 6 and nylon 6,6.

Typical carpet tiles have three layers:

-   -   a. Pile fiber generally made of nylon, polyester or         polypropylene.     -   b. Primary backing, i.e. the textile substrate into which the         pile fiber is tufted. There are two kinds used, namely woven or         non-woven. An adhesive is applied to glue the pile into the         primary backing. Common adhesives include EVA (ethylene vinyl         acetate) or SBR (styrene-butadiene rubber), among others.     -   c. Secondary backing, i.e. the backing that is applied to the         primary backing after the yarn is tufted into it. Sometimes         there is a fiberglass layer embedded into the secondary backing.         Sometimes there is cloth scrim adhered to the back of the         secondary backing. As used in this specification, unless the         context dictates otherwise, the term “secondary backing” is         intended to include backings that might include fiberglass         and/or that might include additional scrims.

Yarn is tufted into carpet pile in different constructions. Different constructions are realized by adjusted the following variables among other variables:

-   -   a. Stitch Count and Gauge. The gauge is the number of rows of         stitches across the width of the tufting machine. The stitch         count is the number of stitches per inch running along the         length of the carpet. Together the gauge and stitch count         determine the number of tufts per square inch of carpet pile.         The gauge and stitch count for carpet tiles are usually between         8 and 13 per inch.     -   b. Pile Heights. This is the height of the loops of yarn. Some         carpet constructions are level loop (i.e. where all loops are         the same height). Other carpet constructions are multi-level         loop (i.e. where different loops are different heights. Pile         heights on carpet tiles generally vary between ⅛ and ½ of an         inch.     -   c. Pile Weight. This the total weight of pile fiber per square         yard of carpet tile. The pile weight of a carpet tile generally         varies between 14 and 28 oz/yd².

There are many carpet tile secondary backing systems, including for example:

-   -   a. PVC (polyvinyl chloride) secondary backing systems, which         typically include PVC, calcium carbonate or other fillers and         potentially other additives.     -   b. Bitumen backing systems, which typically include bitumen,         calcium carbonate or other fillers and potentially other         additives.     -   c. Polyolefin backing systems such as the one branded as EcoWorx         by Shaw Industries or the one branded as EcoFlex by Mohawk         Industries.     -   d. Polyester backing systems such the one branded as Nexterra by         Beaulieu of America.

There are different flammability standards in different countries:

-   -   a. In North America the principal standard is ASTM E 648.         -   i. With this standard and test method, if a carpet achieves             a critical radiant flux of 0.45 W/cm², then the carpet tile             qualifies as a “Class I”.         -   ii. If however a customer only achieves critical radiant             flux of 0.22 to 0.45 W/cm², then it qualifies as a “Class             II”     -   b. In Europe, the principal flammability testing standard is BS         EN 9239-1:2002         -   i. The highest level is “Bfl’—greater than 8.0 kW/m²         -   ii. The middle level is “Cfl”—greater than 4.5 kW/m²         -   iii. The lowest level is “Dfl”—greater than 3.0 Kw/m²     -   c. In Australia, the standard is AS/ISO 9239.1 2003. The         different levels for flammability are 1.2, 2.2 and 4.5 kW/m²

Within different jurisdictions there are different building codes that specify what class or test level is needed for different types of buildings. If a carpet achieves a higher flammability class then it is permitted to be used in a greater number of applications.

The flammability level of a product is impacted most by the type of fiber used. When nylon fiber is used, then it can be expected the best flammability rating can be achieved no matter what pile constructions and what secondary backing system is used. However, as noted above, nylon fiber is the most expensive.

Other factors which affect the flammability of a carpet tile to a lesser extent are pile construction (i.e. gauge, stitch count, pile height), pile weight and secondary backing system.

It would be advantageous to be able to use less expensive fibers, while still achieving an acceptable or superior flammability rating.

BRIEF SUMMARY OF THE INVENTION

In view of the preceding, the invention provides a carpet tile which uses a novel flame retardant which interacts with the secondary backing system and the pile fiber to achieve superior flammability results.

Specifically, the invention uses Aluminum Hydroxide—Al(OH)₃ as the preferred flame retardant, in the manner described in greater detail below. During combustion the flame retardant will interact with the pile fiber and the secondary backing system. Therefore to have the desired effect a particular flame retardant needs to be included in a particular concentration depending on the pile fiber type, the pile construction, the pile weight and the type of secondary backing system.

Further details of the invention will be described or will become apparent in the course of the following detailed description and drawings of embodiments of the invention, presented as examples only.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described with reference to the accompanying drawing, in which:

FIG. 1 (Prior Art) is a cross-section of a typical prior art carpet.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 (Prior Art) shows a typical prior art carpet, comprising a pile fiber 1, a secondary backing 2, and a primary backing 3 into which the pile fiber is tufted.

As stated above, the preferred embodiment of the invention uses Aluminum Hydroxide (Al(OH)₃) as a flame retardant in the secondary backing 2. However, other embodiments of this invention could use Magnesium Hydroxide (Mg(OH)₂) as the flame retardant and such other embodiments could also put the flame retardant into the pre-coat adhesive on the primary backing instead putting it in the secondary backing.

Due to the interactions with different parts of the carpet tile during combustion, the concentration of Aluminum Hydroxide which should be included in the carpet tile depends on the type of fiber, pile construction, the pile weight and the secondary backing system of the carpet tile. The appropriate concentration for any given carpet tile must be determined by routine experimentation, based on the following guidelines.

In general flammability performance is worse with higher pile weight as compared with lower pile weight. Also in general more, flammability performance is worse with higher and looser constructions (i.e. higher pile heights and lower gauge and stitch counts) as compared with lower denser constructions. Also flammability performance is worse with PVC secondary backing systems as compared to bitumen secondary backing systems. These different factors interact with each other such that some trial and error is needed to come up with an optimization of these different factors.

Specifically, it was determined that with a concentration of 7 oz of aluminum hydroxide per square yard of carpet tile in combination with a bitumen secondary backing system, a pile fiber made of two polypropylene yarns of approximately 1100 decitex twisted together at 1.5 to 2.5 turns per inch, tufted on a 1/10 inch gauge tufting machine with 10 stitches per inch and with uniform pile height of ⅛ inch, a critical radiant flux of greater than 0.45 W/cm² could be reliably achieved when tested according the ASTM E 648 test method. The flame retardant was added to the secondary backing in powder form and mixed in evenly along with the bitumen and the calcium carbonate.

However, in order to achieve a critical radiant flux of greater than 0.45 W/cm^(2,) for carpet tiles using a bitumen secondary backing system and pile fiber having two polypropylene yarns of approximately 1100 decitex twisted together at 1.5 to 2.5 turns per inch, tufted on 1/12 inch gauge tufting machine with 10 stitches per inch and with pile height varying throughout the carpet between 1/16 inch and ¼ inch, a concentration of 9 oz of aluminum hydroxide per square yard of carpet tile was needed.

For any given carpet tile construction, using the teachings of this invention, it is only necessary to conduct routine experimentation to determine the appropriate concentration of the chosen flame retardant and chosen location of application (i.e. secondary backing or pre-coat adhesive on the primary backing).

It will be evident to those knowledgeable in the field of the invention that many variations on the examples described above are conceivable within the scope of the invention. It should therefore be understood that the claims which define the invention are not restricted to the specific examples described above. Possible variations include, for example, the use of different flame retardants and in different concentrations optimized for used with different pile fibers, pile constructions and different secondary backing systems in order to achieve different flammability standards.

Further variations may be apparent or become apparent to those knowledgeable in the field of the invention, within the scope of the invention as defined by the claims which follow. 

1. A carpet tile system comprising a pile fiber made of polypropylene, tufted into a primary backing that is combined with a secondary backing system, which includes a flame retardant in at least one of (a) the secondary backing system and (b) the pre-coat adhesive on the primary backing, the flame retardant provided in a sufficient concentration to achieve an ASTM E 648 Class I flammability rating.
 2. The carpet tile system of claim 1 wherein the secondary backing system is a bitumen based secondary backing system.
 3. The carpet tile system of claim 1 wherein the secondary backing system is a PVC-based secondary backing system.
 4. The carpet tile system of claim 1 wherein the secondary backing system is a polyolefin-based secondary backing system.
 5. The carpet tile system of claim 1 wherein the secondary backing system is a polyester-based secondary backing system.
 6. The carpet tile system of claim 1 wherein the flame retardant is Magnesium Hydroxide Mg(OH)₂.
 7. The carpet tile system of claim 1 where in the flame retardant is Aluminium Hydroxide Al(OH)₃.
 8. A carpet tile system comprising a pile fiber made of polyester, tufted into a primary backing that is combined with a secondary backing system, which includes a flame retardant in at least one of (a) the secondary backing system and (b) the pre-coat adhesive on the primary backing, the flame retardant provided in a sufficient concentration to achieve an ASTM E 648 Class I flammability rating.
 9. The carpet tile system of claim 8 wherein the secondary backing system is a bitumen based secondary backing system.
 10. The carpet tile system of claim 8 wherein the secondary backing system is a PVC-based secondary backing system.
 11. The carpet tile system of claim 8 wherein the secondary backing system is a polyolefin-based secondary backing system.
 12. The carpet tile system of claim 8 wherein the secondary backing system is a polyester-based secondary backing system.
 13. The carpet tile system of claim 8 wherein the flame retardant is Magnesium Hydroxide Mg(OH)₂.
 14. The carpet tile system of claim 8 where in the flame retardant is Aluminium Hydroxide Al(OH)₃.
 15. A carpet tile system comprising a pile fiber made of polypropylene or polyester, tufted into a primary backing that is combined with a secondary backing system, which includes a flame retardant in at least one of (a) the secondary backing system and (b) the pre-coat adhesive on the primary backing, the flame retardant provided in a sufficient concentration to achieve a superior rating to the rating normally achieved on a carpet tile with polyester or polypropylene pile fiber.
 16. The carpet tile system of claim 15 wherein the secondary backing system is a bitumen based secondary backing system.
 17. The carpet tile system of claim 15 wherein the secondary backing system is a PVC-based secondary backing system.
 18. The carpet tile system of claim 15 wherein the secondary backing system is a polyolefin-based secondary backing system.
 19. The carpet tile system of claim 15 wherein the secondary backing system is a polyester-based secondary backing system. 